The invention relates to a system for a convertible vehicle in general and in particular to an anti-trapping sensor for sensing an object in the pivoting range of a top of a convertible vehicle. The invention further relates to a method for sensing a top of a convertible vehicle which is moved by a drive.
From practice it is known to assign sensors to a top of a convertible vehicle, which top is mounted on a bodywork of a motor vehicle in such a way that it can be moved, in particular pivoted, and which passes through a pivoting range during the movement, said sensors monitoring the top during the movement and what are referred to as anti-trapping sensors, which sense whether between the top of the convertible vehicle and the bodywork there are objects which could be trapped when the top of the convertible vehicle comes to rest on the bodywork are known in the pivoting range of the top for a convertible vehicle. It is also known to provide anti-trapping sensors between linkage parts of the top for a convertible vehicle which can be moved in relation to one another, for example between two roof links which are rotatably coupled to one another or folding roof bows which are guided by the roof links, with the roof links or bows which are coupled to one another carrying out scissor-like rotational movement when the top comes to rest so that an object could be trapped between the roof links and the bows.
German patent application DE 103 05 342 A1 describes a system and a method for sensing an object in the pivoting range of the top of a convertible vehicle. The system comprises here a top to which an electrode device for sensing electrical field properties is assigned and which comprises an evaluation unit for evaluating the sensing field properties. An electrode which is embodied as a wire and as a capacitive pickup, and which is completely assigned to the top, is described. One end of the wire is connected to a frequency-determining capacitor, with two oscillators generating an identical frequency provided that an object does not approach the wire. If an object enters the vicinity of the wire, the capacitance of a capacitor changes so that the two oscillators are detuned with respect to one another, with a low frequency signal being generated which is detected and evaluated in order to control a drive of the top. An electronic system which is connected downstream provides, in particular, the possibility of zero adjustment in order to rule out incorrect alarms and to counteract drifting between the two oscillators. The anti-trapping sensor is embodied here as a unit which is assigned to the top of the convertible vehicle and is independent of the top of the convertible vehicle. The top of the convertible vehicle serves here essentially only as a carrier for the anti-trapping sensor to which said sensor is attached and by which the sensor is guided. It is disadvantageous that the wire is adapted specially to the geometry of the top and is to be provided as a component which is additional to the actual top of the convertible vehicle. It is also disadvantageous that if the wire is damaged or destroyed, it fails easily and supplies inaccurate results so that the system fails overall. It is also disadvantageous that the system for sensing the movement of the top is in its entirety inadequate to such an extent that the wire would have to surround all of the surface of the entire top, which requires a very complex design.
German patent application DE 102 48 761 A1 describes a sensor which measures in a capacitive fashion as an anti-trapping device for convertible-vehicle tops which are in particular operated automatically, with the sensor being constructed in a planar and film-like fashion with a carrier which is formed from film material, and with the dielectric being air. A detection device with an arrangement of four capacitive sensors, which are each embodied as a planar and film-like sensor and on which electrodes are arranged on a film material as carrier, is illustrated explicitly. In addition to the sensors which operate in a capacitive fashion, the detection device can also comprise sensors of other types, in particular optical sensors. It is disadvantageous that the sensors have to be provided in addition to the top for the convertible vehicle, thus constituting additional expenditure for the manufacture of the top for a convertible vehicle. The film-like sensors may prove susceptible to faults and wear in use over time. It is also unfavorable that the film-like sensors cause heat to accumulate in the interior of the convertible vehicle, which is problematic in particular in hot climatic conditions.
German patent application DE 198 36 056 A1 describes a capacitive detection device for a top for a convertible vehicle which can in particular be driven automatically, with the detection device comprising an electrically conductive transmitter surface on one side and a metal surface with a sensor wire on the other, an alternating current signal, which is tapped by the sensor wire and evaluated, being applied to the electrically conductive transmitter surface. Such a detection device is complex and also problematic in terms of insulation and visual concealment owing to the exposed metal face.
German patent application DE 40 04 353 A1 describes a proximity sensor as an anti-trapping device for window panes of motor vehicles having an ultrasonic sound sensor, infrared sensor, heat sensor or inductive sensor instead of a capacitive sensor. Such a proximity sensor is also hardly suitable for the top for convertible vehicles since the region to be monitored is very large, the top for a convertible vehicle describes a complicated movement sequence and the configuration or open-/closed-loop control of the sensors is very complex.
European patent application EP 0 856 425 A1 describes an anti-trapping device for window panes of motor vehicles having a capacitive sensor with a strain element in the form of a helical spring whose extension or compression changes an electrical resistance in such a way that a trapping situation can be sensed. It is disadvantageous that a trapping situation is not detected until the helical spring has experienced an appreciable extension or compression, that is to say not until a body part has already been trapped. Such an anti-trapping sensor which, in addition, is of complex design, is not suitable in view of the large forces which occur in tops of convertible vehicles.
German patent application DE 102 20 187 A1 describes a device for detecting an obstacle in an opening range of a movable closing element, in particular a motor-operated window pane or a sunroof, with a sealing profile being provided in which a sensor which senses an electric field is provided. The electric field is brought about by an electrical conductor which is fixed to the bodywork. As an alternative to the window pane, it is also possible to provide, as closing elements, a sunroof, a tailgate or a trunk lid; a top for a convertible vehicle is not explicitly specified. However, for a top for a convertible vehicle it is to be noted that its movement sequence is significantly more complicated than the simple linear or rotary movement of sunroofs or hinged flaps so that the described device cannot be readily transferred to tops for convertible vehicles.
German patent document DE 102 20 725 C1 describes a device for detecting an obstacle in an opening range of a movable closing element of a motor vehicle, in particular a motor-operated window pane with a sensor for an electric field, with the pane being insulated with respect to the sensor by means of conducting means in such a way that the moving pane does not influence the electric field and the changes in the electric field are essentially only due to obstacles so that the evaluation is simplified. In particular with respect to tops for convertible vehicles, it is disadvantageous that they have a significantly more complex movement sequence than an essentially linearly displaceable window pane so that insulation cannot be provided easily.
German patent application DE 102 26 133 A1 describes an arrangement for a device for detecting an obstacle in an opening range of a movable closing element, in particular an electrically driven window pane or a sunroof. The device comprises a sensor electrode which generates an electric field in the opening range and whose capacitive changes are sensed by an evaluation device. The sensor is described explicitly only for a window pane or for a sunroof and cannot be transferred to a top for a convertible vehicle without considerable expenditure.